In electrophotography, also known as Xerography, electrophotographic imaging or electrostatographic imaging, the surface of an electrophotographic plate, drum, belt or the like (imaging member or photoreceptor) containing a photoconductive insulating layer on a conductive layer is first uniformly electrostatically charged. The imaging member is then exposed to a pattern of activating electromagnetic radiation, such as light. The radiation selectively dissipates the charge on the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image on the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the imaging member directly or indirectly (such as by a transfer or other member) to a print substrate, such as transparency or paper. The imaging process may be repeated many times with reusable imaging members.
Although excellent toner images may be obtained with multilayered belt or drum photoreceptors, it has been found that as more advanced, higher speed electrophotographic copiers, duplicators, and printers are developed, there is a greater demand on print quality. The delicate balance in charging image and bias potentials, and characteristics of the toner and/or developer, must be maintained. This places additional constraints on the quality of photoreceptor manufacturing, and thus on the manufacturing yield.
Imaging members are generally exposed to repetitive electrophotographic cycling, which subjects the exposed charged transport layer or alternative top layer thereof to mechanical abrasion, chemical attack and heat. This repetitive cycling leads to gradual deterioration in the mechanical and electrical characteristics of the exposed charge transport layer. Physical and mechanical damage during prolonged use, especially the formation of surface scratch defects, is among the chief reasons for the failure of belt photoreceptors. Therefore, it is desirable to improve the mechanical robustness of photoreceptors, and particularly, to increase their scratch resistance, thereby prolonging their service life. Additionally, it is desirable to increase resistance to light shock so that image ghosting, background shading, and the like is minimized in prints.
Providing a protective overcoat layer is a conventional means of extending the useful life of photoreceptors. Conventionally, for example, a polymeric anti-scratch and crack overcoat layer has been utilized as a robust overcoat design for extending the lifespan of photoreceptors. However, the conventional overcoat layer formulation exhibits ghosting and background shading in prints. Improving light shock resistance will provide a more stable imaging member resulting in improved print quality.
Despite the various approaches that have been taken for forming imaging members, there remains a need for improved imaging member design, to provide improved imaging performance and longer lifetime, reduce human and environmental health risks, and the like.
In particular, there is an intense competitive pressure to extend the life of xerographic photoreceptors via protective overcoat layers. It is desired that the overcoat layer reduce surface wear rate, improve scratch resistance, reduce torque and prevent CRU component failure, all in an effort to extend the functional life of the photoreceptor and CRU. Drawbacks of employing a protective overcoat layer include an almost inherent negative impact on electrical performance, ghosting, light shock, and cleaning blade interactions.
One very unique and successful approach is the use of Fluorinated Structured Organic Film (FSOF) as overcoats. This overcoat design is a low surface energy SOF that has proven to extend CRU life dramatically through a combination of low wear rate and low surface energy.
Conventional processes for forming FSOF layers generally include dissolving molecular building blocks in a solvent with a catalyst to create a liquid coating formulation. The liquid formulation is subsequently applied to a substrate creating a wet layer. The wet layer is heated to fully and uniformly react the molecular building blocks and dry the layer to create an FSOF that is fully cross-linked throughout its bulk. Known FSOF layer compositions are described in U.S. Pat. No. 8,247,142, and U.S. Pat. No. 8,372,566, the disclosures of both of which are incorporated herein by reference in their entirety.
However, there still remains an unwanted negative impact on electrical performance and thus there is a need to improve the electrical performance of FSOF films without impacting the life extension performance this technology offers.